The terms "paint stripper" and "paint remover" as used in this application refer to chemical compositions which can strip or facilitate stripping of coatings such as paint which are used to protect and beautify substrates. With the introduction of new and more durable types of synthetic resins and polymers in protective and decorative coatings, the problem of stripping the coating has become increasingly difficult. Prior art paint removers and strippers typically contain blends of aromatic solvents, ketones, paraffin, methanol and diluents, for example, mineral spirits. Traditional paint strippers have contained hazardous materials such as phenol, toluene and methylethyl ketone, and the most effective paint strippers were based on methylene chloride as the primary solvent. Methylene chloride is a very effective solvent, and paint strippers containing methylene chloride are effective for quickly softening most types of paints. Methylene chloride, however, is a highly volatile liquid thereby shortening the work life. In addition, methylene chloride has been discovered to cause tumors and cancer in animals in laboratory tests and, accordingly, attempts are being made in the industry and by governmental regulatory agencies to eliminate or greatly reduce its use.
A number of paint removers and paint strippers have been introduced in recent years which avoid the use of methylene chloride and flammable, volatile and toxic chemicals such as benzene, toluene, phenol, acetone, etc. N-methyl-2-pyrrolidone (NMP) has been employed in place of methylene chloride as a solvent ingredient in paint-stripper compositions as suggested in several patents. U.S. Pat. No. 4,759,510, for example, describes a paint stripper having a low volatility which includes about 20% to 90% by weight of NMP and 30% to 70% by weight of an aromatic hydrocarbon solvent. U.S. Pat. No. 4,836,950 describes liquid formulations for removing screen printing inks which comprises a mixture of NMP and gammabutyrolactone.
U.S. Pat. No. 5,124,062 describes paint-stripper compositions having high flash points and low-boiling volatile organic chemicals which comprise a mixture of a terpene compound containing at least 10 carbon atoms, NMP and a terpene emulsifying surfactant.
Recently, non-hazardous products for removing paint have been introduced which incorporate the use of benzyl alcohol as a principal solvent. The performance of benzyl alcohol-based strippers is improved when activated with an acid, but such stripping agents may deleteriously affect high strength steel which is used, for example, in aircraft landing gear parts. Benzyl alcohol-based strippers also have been available which contain an alkaline component rather than an acid for activation.
EP Patent Application 497,130 A2 describes paint-stripper formulations containing a solvent system comprising an ester of a benzyl or methyl benzyl alcohol. In particular, the formulations comprise benzyl alcohol/benzyl formate/formic acid, and such formulations are reported to strip polyurethane and epoxy paint systems more than 2.5 times as fast as equivalent benzyl acetate/benzyl alcohol/acetic acid formulations.
Paint strippers and paint removers are utilized in the aerospace industry for removing paints from commercial and military jet aircraft. Periodic paint removal is required for aesthetic reasons, for a change of colors, or more importantly, for inspection of the air frame as required for safe operation of an aircraft.